Dokurojō 髑髏杖 Staff with Human Skull in the hands of Kannon Bosatsu
鬼神を降伏する. Conquers demons and demonic influences.
Symbolizes the impermanence of life.
A simile for people who are free from discriminating thoughts. Ikkyuu Soujun 一休宗純 (1394-1481), the renowned Zen monk (and poet) of Daitokuji Temple 大徳寺 in Kyoto, reportedly wandered about during new year celebrations brandishing a staff surmounted by a human skull in his effort to remind people of their thin grasp on life. - reference : Mark Schumacher -

At the riverpool あいのかま Ainokama in the gorge 鮎川の蛇喰 Jabami valley of the river Ayugawa there lived a wicked 悪鬼王 Demon King, who took human lives for his offerings.
The hero Yamato Takeru came to punish him.

鬼神伝説 - The Kishin legend of Onizawa
There is a legend in Onizawa describing a benevolent Oni, more of a mountain-man than a demon.
As the story goes, the Oni was a friend of a villager 弥十郎 Yajuro, and offered to assist in the construction of a dam to collect water for his rice paddies. He did so under the condition that no-one watched him as he worked. Naturally, the villager’s wife breaks the rule by sneaking over to spy on the Oni. The Oni runs away, never to appear again; however, he leaves in such a hurry that he forgets all of his tools. The metal remains of these massive ogre-sized tools — a saw, an ax, a hoe, etc — are now collected and displayed at the Oni shrine in Onizawa.
(Told by Joshua Solomon). oniko, oni-ko 津軽の鬼子伝説 Tsugaru Oniko Legends .

Other places related to the Oni in Onizawa
鬼の腰掛け柏
鬼の土俵

The villagers in Onizawa have a fond relationship with this Oni Deity - 鬼が神様なのである.
At Setsubun, they do not throw beans to drive the Oni away.
At the Boy's festival they do not thatch the roof with mugwort and iris to drive the Oni away.

The Oni here might have been some outlaws in hiding or even Koreans in hiding, which Tamuramaro expelled.

noomen 能面 Noh Theater masks - quote -
This is assumed to have appeared in the early stage of the history, describing supernatural substances such as demons or Tengu (long-nosed goblins). It is distinguishable by its forceful and wild appearance, and roughly classified into two types; 飛出 Tobide portraying demons or savages, and 癋見 Beshimi portraying goblins such as Tengu.- source : the-noh.com/sub/jp/index ... -